To study the effect of differentiation antagonizing non-protein coding RNA (lncRNA DANCR) on the resistance of rectal cancer cells to radiotherapy and explore its possible mechanism. Methods Ninety specimens of rectal cancer patients were selected for neoadjuvant treatment in our hospital. qRT-PCR was used to detect the expression level of DANCR in rectal cancer and paracancerous tissues, and statistically analyze the relationship between DANCR expression and patients' radiotherapy resistance and clinicopathological parameters. Survival analysis was used to analyzed the influence of DANCR expression on the prognosis of patients. HT29 cells were cultured routinely, and the HT29 radiation-resistant cell line (HT29-R) was established using fractional radiation dose escalation, MTS was used to detect the radiotherapy sensitivity of HT29 and HT29-R cells, and qRT-PCR was used to detect the expression of DANCR in HT29 and HT29-R cells. HT29-R cells were divided into control group (si-NC group) and interference DANCR expression group (si-DANCR group) and were transfected with corresponding siRNA. MTS was used to detect the influence of interference DANCR on the sensitivity of HT29-R cells to radiotherapy. Cells in the si-NC and si-DANCR groups were exposed to radiation. Plate clones were used to detect the plate cloning ability of each group cells. Flow cytometry was used to detect the cell cycle and apoptosis rate of each group. Western blotting was used to detect the expression of cell cycle related proteins cyclinD1, CDK4, CDK6 and apoptosis-related proteins caspase 3, Bcl-2, Bax in each group of cells. Results The expression of DANCR in rectal cancer tissues was significantly higher than that in adjacent tissues. The expression of DANCR was related to the TNM staging and radiotherapy sensitivity of rectal cancer patients (P＜0.05). Patients with high DANCR expression had a poorer prognosis (P＜0.05). Compared with HT29 cells, the radiation resistance of HT29-R cells were increased (P＜0.05), and the expression of DANCR in HT29-R cells were increased (P＜0.05). Interference with DANCR enhances the radiotherapy sensitivity of HT29-R cells (P＜0.05). Under the action of radiation, compared with the si-NC group, the plate clone formation ability of si-DANCR group HT29-R cell was reduced (P ＜0.05), the cell cycle was arrested in the G2/M phase, and the apoptosis rate was increased (P＜0.05), the expression of cycle-related proteins cyclinD1, CDK4, CDK6 were decreased, the expression of apoptosis-related proteins caspase 3, Bax were increased, and the expression of Bcl-2 protein were decreased (P＜0.05). Conclusion DANCR increases the radiotherapy sensitivity of rectal cancer cells by regulating cell cycle and apoptosis-related proteins, and is a potential target for the treatment of rectal cancer.